1. Field of the Invention
Example embodiments of the present invention generally relate to a method of repairing a semiconductor device, and a circuit to verifying the repair, and more particularly, to a method of repairing a semiconductor device by verifying a programming of a fuse, and a circuit to verify the fuse programming.
2. Description of the Related Art
A manufactured semiconductor memory device having a defective memory cell may not operate properly and the defective semiconductor memory devices may be discarded. Considering production yield, however, discarding semiconductor memory devices having only a few defective memory cells may not be cost effective. Accordingly, when a semiconductor memory device has only a few defective memory cells, the defective memory cells may be repaired by replacing the defective memory cell with redundant memory cells, which may be designed into the semiconductor memory device.
In general, a repair operation using the redundant memory cell may be performed in such a way that a spare row and a spare column are provided at fixed cell array intervals, and defective memory cells are replaced with the spare memory cells on a row/column basis. For example, when a defective memory cell is detected after a wafer process, a programming operation to replace a defective address with an address of a corresponding spare cell may be performed by an internal circuit. Accordingly, when an address signal corresponding to a defective line may be input during an actual operation, a spare line is accessed instead of the defective line.
In the conventional art, a fuse may be used during a programming operation to replace a defective memory cell with a spare memory cell. In order to perform the programming operation, several methods have been used, for example, a method of cutting off the fuse by applying an overcurrent thereto, a method of burning and cutting the fuse by applying a laser beam thereto, a method of interconnecting junctions by using a laser beam, and a method of programming for example an erasable programmable read-only memory (EPROM). Among the above methods, the laser cutting method has been widely used, because the method is simple and reliable. This method may use a fuse made of a polysilicon wire or metal wire.
However, the laser cutting method is usually performed to repair a defective semiconductor memory device at a wafer level, and may be difficult to use when a defective memory cell is detected at a package level.
In order to solve the above problem, an anti-fuse capable of being programmed at a package level has been proposed.
In general, an anti-fuse may have a higher resistance in an non-programmed state but may have a low resistance in a programmed state. An anti-fuse may be configured to include two conductive layers and a dielectric layer interposed between the conductive layers. The dielectric layer may be made of a dielectric material such as SiO2, silicon nitride, tantalum oxide, and silicon dioxide-silicon nitride-silicon dioxide (ONO). An anti-fuse may be programmed in such a way that a high voltage is applied between both terminals of the anti-fuse to destroy the dielectric layer between the two conductive layers. Accordingly, the programmed anti-fuse may have a lower resistance between both of its terminals.
Address fuses corresponding to word lines and master fuses corresponding to the address fuses may be used to repair a defective semiconductor memory device. That is, the address fuses may be programmed to correspond to an address corresponding to a defective word line, wherein a spare line is selected when the address may be selected. Also, a master fuse corresponding to the programmed address fuse is programmed to allow the programmed address fuse to be used. If the master fuse is not programmed to allow the programmed address fuse to be used, the cell repair operation through the programmed address is not completed.
In a conventional fuse programming method to repair a defective cell, the address fuse and the master fuse are usually simultaneously programmed. Accordingly, if the semiconductor memory device does not operate normally after the fuse programming operation, it may be difficult to determine which fuse was not properly programmed. This problem may become more serious when the semiconductor memory device requires repair at a package level using an anti-fuse.